The present invention relates to a method and system for destruction of biological tissues and/or cells via selective ionization and, more particularly, to a method of ionizing biological tissues and/or cells using metallic nano-particles and electromagnetic irradiation.
Cancer is a major cause of death in the modern world. Effective treatment of cancer is most readily accomplished following early detection of malignant tumors. Most techniques used to treat cancer (other than chemotherapy) are directed against a defined tumor site in an organ, such as brain, breast, ovary and colon tumors, etc. When a mass of abnormal cells is consolidated and is sufficiently large, either surgical removal, destruction of the tumor mass using either heating, cooling, radiative or chemical ablation becomes possible because the target is readily identifiable and localizable. However, it is not uncommon for a cancer that has initially occurred at a primary site to metastasize and spread into adjacent organs as diffuse clusters of abnormal cells. These small clusters of cells, which are more properly referred to as microscopic diffuse metastatic deposits, are not localizable and are virtually impossible to treat other than by systemic chemotherapy or radiotherapy. Yet, because of the diverse nature of cancer cells, only a portion of the metastatic abnormal cells will likely be susceptible to chemotherapy or radiotherapy, leaving abnormal cells that are resistant to the therapy to multiply until the patient dies from the concomitant effects of the malignant cells.
Recently, light and more specifically laser light has been used for non-invasive detection as well as destruction of malignant cells. Laser technology has found many applications in medicine and biology including destruction of cells or tissues, e.g., for the purpose of cancer treatment. Destruction of unwanted cells can be achieved either through a direct interaction between the laser beam and the tissue, or through activation of some photochemical reactions using light-activated molecules which are injected into or otherwise administered to the tissue.
Photo-dynamic therapy (PDT) is a relatively new approach for treating many cancers. At the first step of treatment, one or more drugs that bind to rapidly dividing cells are administered either directly to a tissue or organ or systemically to the treated subject. The drugs administered for PDT are commonly known as photosensitizers due to their inherent ability to absorb photons of light and transfer that energy to oxygen which then converts to a cytotoxic or cytostatic species. Approximately 24-48 hours after the injection, a narrow-band laser is used to excite the photosensitive drug, inducing a chemical reaction which results in a production of free radicals and/or other reactive products that destroy the abnormal tissue or cell with relatively small damage to the surrounding healthy tissue.
To date, PDT has been used to treat esophageal cancer, early stage lung cancer, Kaposi's sarcoma, an AIDS related condition, atherosclerotic plaques, lesions of surface skin diseases, overgrowth of blood vessels in the eye (macular degeneration) and unwanted pathogens in the blood.
The effectiveness of the PDT process depends on the amount of photosensitizer at the target, the absorption properties of the environment neighboring the target and photosensitizer, and a number of physiologic factors such as temperature, pH, oxygen content, and the sensitivity of the target to the photosensitizer generated reaction.
Known PDT techniques suffer from a number of drawbacks and limitations. It is necessary to deliver a large amount of light radiation to the tumor at specific wavelengths to activate the photosensitive agent. Most photosensitive agents are activated at wavelengths that can only penetrate through three or less centimeters of tissue. Hence, non- or minimal-invasive PDT can be used for cancerous growths that are on or near the surface of the skin, or on the lining of internal organs.
Typical prior art PDT light delivery systems have used monochromatic lasers in combination with fiber optic catheters, for example by providing a monochromatic light to a fiber optic bundle, which in turn transmits the light through a light diffuser to the tumor. One disadvantage of such PDT delivery system is that a typical fiber optic catheter transmits only about 30% to 50% of available light energy. Additional energy losses occur in the diffuser which surrounds the light-emitting end of the catheter and diffuses the light emanating from the catheter. The blood and the surrounding tissue also attenuate a substantial portion of the input power. The net result is that only about 25% to 30% of the power is available to activate the photosensitive agent. Besides increasing the required size and cost of the light source, these energy losses also reduce the effectiveness of the treatment since the depth of radiation penetration into the tissue is reduced. With reduced penetration, surgical techniques are required to remove much of the malignant tissue before photodynamic therapy commences, and the likelihood that all malignant tissue is destroyed is lessened.
Another drawback of PDT techniques is that the photosensitizing drug remains in the bloodstream for six weeks or more, causing patients to be extremely light sensitive during that time period.
The present invention provides solutions to the problems associated with prior art cell destruction techniques.